Email Subject Lines: New Data

Recently, MailChimp, the most objectively awesome email marketing software on the planet, completed a study on subject lines compiled from 24 billion delivered emails. If you appreciate data analysis driven from incredibly large sample sizes, that should have gotten your attention.

After parsing the data from literally billions of subject lines, MailChimp ran a regression analysis and published a list of words which either increased or decreased open rates in “standard deviations from the mean.” That’s right: MailChimp found out which words increase or decrease the likeliness an email will be opened, and they shared some of the key findings. Because MailChimp.

Many of the findings reinforce long-held best practice tips. For example, it is generally understood that personalization, such as adding the recipient’s name, yields both higher open rates as well as greater conversion. Likewise, you do not have to search long online to find blog posts extolling the virtues of time-sensitive language.

But, who knows what kind of research underlies those tips. Personally, I find it incredibly reassuring when best practice tips are backed by statistical analysis from giant data sets. Remember, we’re talking “billions” with a “b.” That’s authority.

1. Free

The word “free” had no meaningful effect on open rates, but the word “freebie” drove opens. It is worth noting that the word “Free” is recognized as a trigger in many SPAM filters. So while the word “free” is already not recommended for deliverability purposes, it turns out the word has very little utility in subject lines.

2. Reminders

The word “reminder” had a significant negative impact on open rates, but just add an “s” and you have “reminders,” which greatly increased opens. Statistical analysis on huge data sets always results in some completely inexplicable and counter-intuitive results, and this is my favorite example of that phenomenon. Although, I would assume the word “reminders” is used far less often than “reminder.”

3. Invit…

Invitation, Invites, Invite, and Invited. It doesn’t matter how you say it, invitations get opened. The data proves it.

4. Cancelled

Unless you are in the restaurant industry, never put the word “cancelled” in the subject line of an email. That is, if you want it to be opened. I guess people do not like bad news because across most industries, the word “cancelled” had a significant negative effect on open rates.

5. Urgent

Words that imply time-sensitivity have a positive impact on open rates, with good old “urgent” increasing open rates by an almost full standard deviation. However, a word of caution: The word “urgent” does not just denote time-sensitivity. It is worth remembering that “urgent” could also imply a sort of emergency. Be careful not to create the wrong expectation with your subject lines. If you say something is urgent in the subject line, the email better corroborate that message. (A topic for another post)

Thank You!

Finally, you probably won’t be surprised to learn that one of the best performing word combinations is “thank you.” It may be that people appreciate the courtesy of a thank you message or maybe they are opening the email to confirm a transaction has been processed. Bottom line: It pays to say thank you.